Mumbai (Bombay) and other Indian cities have woken up to a state of high alert after three blasts shook the commercial capital, killing¹ 18 and hurting dozens.

印度商业中心孟买发生三起爆炸案，18人死亡，数十人受伤，孟买以及其它城市随机进入高度戒备状态。

The attack took place at evening rush hour on Wednesday
Indian PM Manmohan Singh appealed to the people of Mumbai "to remain calm and show a united face".

Later the United Nations strongly condemned² Wednesday's attack, describing it as "heinous³（可憎的） ".

No group has said they carried out the attack, which took place in three districts during evening rush hour.

India's Home Minister P Chidambaram has said he believed the blasts were "a co-ordinated attack by terrorists", as the explosions occurred within minutes of one another.

"All groups that have capacity to carry out such terror attacks are suspect. All angles will be investigated, all leads will be followed. I appeal to people not to speculate（推测，投机） ," he told reporters.

The attacks are the deadliest in Mumbai since November 2008 when 10 gunmen launched a three-day co-ordinated raid in which 166 people were killed.

'Home-made bombs'

One explosion was reported in the Zaveri Bazaar⁴, another in the Opera House business district and a third in Dadar district in the city centre.

All three bombs were reported within a 15-minute period, starting at around 1850 local time (1320 GMT).

They were placed in a bus stand, on the road and on a motorcyle respectively at the three sites.

The explosion in the Zaveri Bazaar area was of low intensity⁵, while the blasts at Opera House and Dadar were "of medium to high density⁶", Mr Chidambaram said.

The BBC's Rajini Vaidyanathan: "Everyone is shocked"

Federal commando, forensic⁷（法院的） and investigation⁸ teams have arrived in Mumbai to help the local police.

The capital, Delhi, Calcutta and several other cities have also been put on alert, with a police presence being stepped up at public places like malls, cinemas, parks and transport terminals.

On Thursday, the government revised the death toll⁹ from the blasts down from 21 to 17, and said 131 people had been injured.

But rescue workers also found a severed¹⁰ head at one of the blast sites which had not yet been identified or included in casualty figures, Mr Chidambaram said.

Peter Wittig, the current president of the UN Security Council, said members of the UN body condemned the attack "in the strongest terms".

"They expressed their deep sympathy and sincere condolences（慰问） to the victims of these heinous crimes and acts and to their families and to the people and government of India," he said.

"The Security Council is determined¹¹ to combat all forms of terrorism," he added.

The biggest explosion occurred at the Opera House in an area known as a hub for diamond traders.

One witness said he had tried to help by getting the wounded onto motorbikes to take them to hospital.

"We came outside, and the area was filled with black smoke. There were bodies lying all over the street, there was lots of blood... We saw many bodies missing arms and missing legs," Aagam Doshi told Reuters news agency.